util/tev_curl: Fix double free error in schedule_fd_processing()
Prevents deletion of already executed timer.
libcurl calls schedule_fd_processing every time it wants to have (new)
timer setup. And it happens quite a lot of times.
Being called schedule_fd_processing wants to delete previous timer before
creating new one. That's basically proper action. The problem is it sometimes
tries to delete non-existent (already executed and deleted by libtevent)
timer. This is "double free" case.
Proposed patch sets timer pointer in tcurl_ctx to NULL at the end of timer
handler (actually can be placed anywhere in the handler: handler called =>
timer deleted by libtevent). That prevents schedule_fd_processing from
freeing already freed memory. And I think it is good idea overall to not
have pointers to freed memory (dangling pointers). This should be safe
operation since all processes are single-thread proces
Reviewed-by: Jakub Hrozek <email@example.com>